Currently, the frequency bands used for GSM telephone transmission in Europe and America are the following:                900 MHz band (GSM 900 Europe). Encompasses from 880 MHz to 960 MHz, so that the bandwidth from 880 MHz to 914 MHz is used for transmission by the mobile station and the band from 925 MHz to 960 MHz is used for transmission by the base station.        1800 MHz band (GSM 1800 Europe). Encompasses from 1710 MHz to 1880 MHz, so that the bandwidth from 1710 MHz to 1785. MHz is used for transmission by the mobile station and the band from 1805 MHz to 1880 MHz is used for transmission by the base station.        1900 MHz band (GSM 1900 USA). Encompasses from 1850 MHz to 2005 MHz, so that the bandwidth from 1850 MHz to 1910 MHz is used for transmission by the mobile station and the band from 1945 MHz to 2005 MHz is used for transmission by the base station.        
In addition, the two main design characteristics for any portable telephone antenna are that it must be mounted within the casing of the portable telephone and that during its operation the set will be handled by a user, who will point it in any direction. As the antenna is placed very near the casing, the antenna current is induced not only in the antenna but also in the conducting part of the casing, so that the original radiation pattern is changed. It is also the case that the efficiency of transmission degrades with the proximity of the human body, as the antenna is affected by the movements of the body. These design requirements are further complicated by having to manufacture the sets as small as possible. It is well known that the efficiency of radiation and bandwidth are degraded with a decreasing antenna size. On top of all of these requirements, considerations such as bandwidth security and diversity of reception must be considered.
Various solutions have been adopted to improve the gain of transmissions affected by the casing, the human body or the location. One of these is described in EP patent 661824, which describes a folding portable telephone in which the antenna is placed in the part that is rotated outwards, so that during transmission it is separated as much as possible from the user's ear in order to reduce as much as possible the gain resulting from the proximity of the human body.
Another solution is that proposed in U.S. patent 2002013159, which describes a folding portable telephone in which the antenna is on the fixed part, so that when the folding part is brought to the user's ear the antenna is separated by a certain angle from the user's head, reducing the loss of gain of the signal due to the proximity of the body.
All of these solutions have in common that they seek to reduce the effect on the transmission gain on the proximity of the human body, yet do not mention improving the signal when it is weak or in a multiroute transmission environment.
Thus, the object of this invention is to improve as much as possible the effective gain in the desired frequency range, allowing to reduce the size and weight of portable telephones while increasing the operation time, allowing using said telephones in areas of low signal intensity and allowing to reduce the transmission power, which allows reducing the battery and thus the weight of the portable telephone, or extending the operation time of the battery.